Chapter 5

The Integumentary System consist of

-skin
-hair
-nails
-sweat glands
-sebaceous glands (oil)

Skin consists of these regions

-epidermis
-dermis
-hyperdermis

Epidermis

-consists mostly of keratinized stratified squamous epithelium
-Superficial region
-epithelial tissue/ avascular

Dermis

-Underlies epidermis
-fibrous connective tissue/avascular

Hyperdermis

-subcutaneous layer deep to skin
-anchors skin to underlying structures and muscles
-not part of the skin
-adipose tissue that absorbs shock/insulin

4 cell types found in the epidermis

-keratinocytes
-melanocytes
-dendritic
-tactile

Keratinocytes

-produce fibrous keratin
-major cells of epidermis
-connected by desmosomes
-millions fall off everyday

Keratin

Proteins that give skin protective properties

Melanocytes

-spider shaped shells located in deepest epidermis
-produce pigment melatonin, which is packaged into melanosomes

Melanosomes

transferred to keratinocytes, where they protect nucleus from UV damage

Dendritic cells

- star shaped macrophage-like cells that patrol deep epidermis
-key activators of the immune system

Tactile cells

sensory receptors that sense touch

Layers of the epidermis (from deepest to most superficial)

-stratum basale
-stratum spinosum
-stratum granulosum
-stratum lucidum (only on thick skin)
-stratum corneum

Thick skin

5 layers (strata) and is found in high-abrasion areas (hands/feet)

Thin skin

Contains 4 layers (strata)

Stratum Basale (basal layer)

-deepest of all layers
-attracted to dermis
-single row of stem cells is mitotic
-10-25% of layer is composed of melanocytes

Stratum Spinosum (prickly layer)

-several layers thick
-cells contain prekeratin filaments attached to desmosomes
-keratinocytes appear spikey

Stratum Granulosum (granular layer)

-4-6 cells deep (cells flattened so layer is thin)
-cell appearances change
-accumulate keratohyaline granules that help form keratin fibers
-accumulate lamellar granules
-cells above the layer are dead

Lamellar Granules

A water-resistant glycolipid that slows water loss

Stratum Lucidum (clear layer)

-found in thick skin
-2-3 rows of dead keratiocytes

Stratum Corneum (horny layer)

-20-30 rows of flat anucleated keratinized dead cells
-3/4 of epidermal thickness
-protect from the environment
-prevent water loss
-protect from abrasion/penetration
-act as a barrier

Parts of the papillary layer

-dermal papillae
-friction ridges

Dermal Papillae (pegs)

Superficial region of dermis that sends finger-like projections up into epidermis

Friction Ridges

-enhance gripping ability
-contribute to sense of touch

Parts of the reticular layer

-cleavage (tension) lines
-cutaneous plexus
-flexure lines

Cleavage Lines

Caused by collagen fibers sunning parallel to skin surface

Cutaneous Plexus

Network of blood vessels between reticular layer and hypodermis

Flexure Lines

Dermal folds at or hear joints

Three pigments contribute to skin color

-melanin
-carotene
-hemoglobin

Melanin

-only pigment made in skins made by melanin
-all humans have the same number of keratinocytes, so color differences are due to amount and form melanin
-freckles and moles are local accumulations of melanin

Carotene

-yellow to orange
-obvious in palms/soles
-accumulates in stratum corneum and hypodermis
-converted to vitamin A

Hemoglobin

pinkish hue of skin due to low levels of melanin

Alterations in skin color that indicate disease

-cyanosis
-erythema
-pallor
-jaundice
-bronzing
-bruises

Cyanosis

-Blue skin color
-low oxygenation of hemoglobin

Erythema

-redness
-fever, hypertension, inflammation

Pallor

-bleaching or pale color
-ahemia, low blood pressure, fear, anger

Jaundice

-yellow color
-liver disorders

Bronzing

inadequate steroid hormones (Addison's disease)

Bruises

-black and blue marks
-clotted blood beneath skin

Hair

consists of flexible strands of dead keratinized cells

Functions of hair

-warn off insects on sin
-hair on head guards against physical trauma
-protect from heat loss
-shield skin from sunlight

Hair regions

-shaft
-root

Shaft

Area that extends above scalp, where keratinization is complete

Root

Area within scalp where keratinization is still going on

3 parts of hair shaft

-medulla
-cortex
-cuticle

Medulla

Central core of large cells and air spaces

Cortex

Several layers of flattened cells surrounding medulla

Cuticle

Outer layer consisting of overlapping layers of single cells

Structure of hair follicle

-hair matrix
-arrector pili
-hair papilla

Types and growth of hair

-vellus hair
-terminal hair

Vellus hair

Pale, fine body hair of children/adult females

Terminal hair

Course, long hair
ex. scalp and eyebrows

Hair thinning/balding conditions

-alopecia
-baldness
-male patterned baldness

alopecia

Hair thinning of both sexes after age 40

baldness

genetically determined and sex influenced

Male patterned baldness

Caused by follicular response to DHT (dihydrotestosterone)

Nails

-scale like modifications of epidermis that contains hard keratin
-free edge, nail plate, and root

Nail matrix

Thickened portion of bed responsible for nail growth

Nail folds

Skin folds overlap border of nail

Eponychium

Nail fold that projects onto surface of nail body
ex. cuticle

Hyponychium

Area under free edge of plate that accumulates dirt

Lunule

Thickened nail matrix, appears white

Parts of the nail

-nail matrix
-nail folds
-eponychium
-hyponychium
-lunule

Two types of sweat glands

-merocrine
-apocrine

Two modified apocrine glands

-ceruminous glands
-mammary glands

Ceruminous glands

Lining of external ear canal; secrete cerumen (earwax)

Mammary glands

Secrete milk

Sebaceous glands

-widely distributed, except for thick skin of palms and soles
-develop from and secrete into hair follicles
-stimulated by hormones

Sebum

-oily holocrine secretion
-bacterial properties
-softens hair and skin

Homeostatic imbalances on the skin

-whiteheads
-blackheads
-acne
-seborrhea (cradle cap)

Whiteheads

blocked sebaceous glands

Blackheads

whiteheads if secretion oxidizes

Acne

infectious inflammation of sebaceous glands

Seborrhea (cradle cap)

overactive sebaceous glands in infants

Functions of skin

-protection
-body temp regulation
cutaneous sensations
-metabolic functions (calcitriol)
-blood reservoir
-excretion of wastes

*keeps things from getting in and out*

Calcitriol

-active vitamin D
-requires UV light
-allow you to absorb calcium

Skin constitutes these three barriers

-chemical
-physical
-biological

Insensible perspiration

If body temp rises, dilation of dermal vessels can increase sweat gland activity

Sensible

-cold external environment
-dermal blood vessels constrict
-skin temp drops to slow passive heat loss

Skin cancer

-most are benign and do not spread
-risk factors include overexposure to UV radiation and irritation of skin

3 major types of skin cancer

-basal cell carcinoma
-squamous cell carcinoma
-melanoma

Basal carcinoma

-least malignant and most common
-stratum basale cells proliferate and slowly invade dermis and hypodermis
-cured 99% of the time

Squamous cell carcinoma

-second most common type
-involves keratinocytes of stratum spinosum
-scaly reddened papule
-surgically removes

Melanoma

Cancer of melanocytes is most dangerous types because it is highly metastatic and resilient to chemotherapy

How to check for Melanoma

ABCD rule
-Asymmetrical
-Border
-Color
-Diameter

Burns

-Tissue damage caused by heat, electricity, radiation or chemicals (denaturation of proteins)
-Threat of dehydration and electrolyte imbalance

First degree burns

-epidermal damage only
-redness swelling and pain

Second degree burns

-epidermal and upper
-blisters appear

Third degree burn

-entire thickness of skin involved
-gray/white, cherry red, or blackened color
-no edema is seen and area is not painful due to destroyed nerve endings

Scar

Collagen fibers hold damaged tissue together